Sends some geological specimens. Describes his recent trips and findings on the geology of the Andes. Asks if HSF has seen large beds of shells on elevated land – possibly at Rio Grande or S. Brazil.
The Beagle will sail in a few days from Callao.— Before leaving the shores of S. America, I am tempted to send you the accompanying specimens.— In themselves they have little value, but I hope you will more readily believe that mere forgetfulness is not the cause of the fewness of their numbers.— Generally speaking in the whole line of coast of Chili, where the Beagle for the last 12 months has been employed, the rocks are Granitic.— It is only in the interior, that the lower Crystalline formations are covered by the Porphyries & Breccias & only in the main Cordilleras, where these are again covered by the Gypseous, Sandstone, Limestones & ancient Lavas.— What I before stated about my manner of travelling, render the collecting even of sufficient specimens, much more duplicate ones extremely troublesome.—
In the latter end of March, I had the satisfaction of crossing the Cordilleras to Mendoza & returning by a different route. It is impossible to imagine more illustrative scenes of subterraneous violence, than these huge mountains present. The strata cracked & fissured by numberless dykes have been tossed about, like the ice on a running stream; there is however a degree of rough parallelism in the lines of disturbance. The scenery is on so grand a scale, & the atmosphere so clear & brilliant, that the whole was to me like entering on a new Planet.— After returning to Valparaiso, I travelled by land to Copiapò, whilst the Beagle was surveying the coast. It was a most dreary journey, in the deserts, which extend to the North of Coquimbo, there is no sort of interest excepting from Geology.— I hope now to be able to give some sort of outline of the superposition of the strata & the structure of the mountains in Chili. It is very certain that the general idea of the Cordilleras being composed solely of Volcanic rocks is quite incorrect. There is one point in the Geology of S. America, in which I am much interested, it is the recent elevation of the land.— That such has taken place & to a considerable amount on this coast I have abundant proofs. Have you ever noticed on land elevated from 30 to 200 ft above the sea, any large beds of marine shells, & which did not appear carried there by man? I think it probable that such might occur at R. Grande or South Brazil; if you have any information on this head, I should be most grateful for such a communication.— My direction in England is Shrewsbury or indeed to the C of Good Hope on my road there. I am afraid you will think me a very troublesome correspondent; I only wish I could send you instead of Geological questions & details, some specimens which would be worthy of your acceptance.—
The Beagle now proceeds direct to the Galapagos, from thence across the Pacifick to Sydney, C. of Good Hope to England.— I confess, I am so little accustomed to these long expeditions, that I look forward to this last stage, with more interest, than the whole of the voyage. I have the pleasure to remain, Your obliged & obedient servant | Chas. Darwin
- f1 284.f1The first two chapters of South America bring together the evidence of the recent elevation of both coasts of the continent. On the east coast the location of shells in formations observed by CD and Orbigny constitutes the main evidence. No evidence from Fox is mentioned.